Spherical polyelectrolyte brushes as nanoreactors for the generation of metallic and oxidic nanoparticles: Synthesis and application in catalysis

If long chains of a polyelectrolyte are densely affixed to colloidal spheres, a spherical polyelectrolyte brush (SPB) results. It has been demonstrated that most of the counterions that balance the charges of the polyelectrolyte chains in aqueous solution are confined within the brush layer. Some years ago it has been shown that metal ions confined within a SPB can be reduced to yield well-defined metal nanoparticles with high catalytic activity. In a similar way, metal oxides as TiO₂ and MnO_x can be generated within the brush layer. Here we review this work with special emphasis on catalysis. We first discuss recent papers that study the confinement of the counterions within SPB and the consequences thereof for the solution properties of the SPB. Then a survey of synthetic studies on these composite particles is presented. Finally, a comprehensive review of the investigations on the catalytic activity of metallic and oxidic nanoparticles generated on SPB will be given. All results obtained on these systems demonstrate SPB act as true “nanoreactors” that can be used for an efficient and safe handling of metallic and oxidic nanoparticles in catalysis without impeding their catalytic activity.